Développement d'un modèle 3D in vitro pour reproduire le processus d'ostéointégration des implants dentaires

Dental implants have been clinically used for almost 5 decades. The success of dental implant depends on the osseointegration, which is the formation of a structural and functional connection between the bone and dental implant. The significant failure rate of osseointegration on long term requires the development of a convenient research model to better understand this process. Based on a systematic review performed during this thesis, we have observed that 3D in vitro models developed to study dental implant integration are limited in number and lack in-depth biological and mechanical characterization of osseointegration. The objective of this thesis was to develop a novel in vitro model of osseointegration to serve as a platform for biomaterials screening. The first aim was to develop and characterize a mineralized hydrogel-based 3D in vitro model to culture cells with osteogenic differentiation potential. The second aim was to incorporate this hydrogel into 3D-printed porous polylactic acid (PLA) scaffold with dental implants to evaluate their osseointegration.For the hydrogel component of the model, methacrylated collagen (ColMA) 0.2%, methacrylated hyaluronic acid (HAMA) 0.5%, methacrylated gelatine (GelMA) 5% were tested. While GelMA5%, showed compromised cell viability after 5 weeks of culture, and ColMA 0.2% showed high shrinkage, ColMA0.2%+HAMA0.5% showed optimal balance between cell viability and gel stability. For cellular component of the model, three cell candidates were tested: SAOS-2, MC3T3-E1, and immortalized MSCs. SAOS-2 could not attach to the hydrogel while MC3T3-E1 cells and immortalized MSCs had a normal morphology, were metabolically active for 5 weeks and mineralized the gel. Immortalized MSCs were chosen for the model as they are human cells and showed higher mineralization than MC3T3-E1 cells. It was shown that culturing those cells in a culture media with elevated calcium concentration accelerated cell-initiated mineralization. Mineral was deposited in the form of spheres with high calcium and phosphate concentration. Osteoblastic differentiation was also shown through increased ALP gene expression and enzymatic activity. Proteomic profiling revealed a collagen-rich extracellular matrix with enrichment of type I collagen. Additionally, there was enrichment of signalling pathways involved in osteoblastic differentiation. When this hydrogel-based model was further integrated into a 3D-printed PLA scaffold with a dental implant, it was shown that cells could migrate, deposit matrix, and initiate mineralization on the dental implant surface. Additionally, a sensitive pull-out test was specifically developed for the model to detect the attachments initiated by the cells by measuring the force needed to remove the implant from the model.This thesis describes the development of a new 3D in vitro model for dental implant research using a hydrogel-based mineralized bone model that is thoroughly characterized for osteogenic differentiation and mineralization. Additionally, the model was the first to combine 3D-printed polysynthetic scaffold and hydrogel-embedded cells to perform mechanical testing of osseointegration in vitro. The versatility of this model highlights its potential in revolutionizing dental implant screening by overcoming the low complexity of 2D in vitro models and interspecies variability of in vivo models.